Magnetic resonance microscopy (MRM), including microscopic imaging and spectroscopy are becoming increasingly important in cancer diagnosis and treatment. Both morphometric and metabolic changes in cells can be detected with MRM which may assist in early evaluation of therapeutic response. However, the results are often ambiguous due to heterogeneity of responses and the long measuring times circumvent the potential for following dynamic cellular processes. To improve this situation, we propose to develop and test a microscope in which proton MRM and optical microscopy (OM) can be performed simultaneously to study heterogeneous mammalian cell populations. With this technology, information from OM measurments will be used to guide MRM measurements, significantly improving the speed and accuracy by which MRM measurements can be obtained. High resolution OM (fluorescent) images will be used to select a subpopulation of cells undergoing a physiological response. These OM images will then be used to guide MRM experiments such that water images and metabolite spectra are obtained from only the cells of interest within the population. In the R21 phase of this proposal, an integrated OM/MR microscope in which 2 or more monolayers of cultured human cells growing within a perfusion system will be designed, constructed and tested. Each layer will have a field of view of 1 mm2. The probe will operate in a standard wide-bore (89 mm) vertical magnet with a field of 11.7 Tesla. Our goal is that this probe will be able to determine OM images with 1.5 muM spatial resolution in seconds, and measure proton MR metabolite spectra of 1,000-2,000 randomly distributed human cells within 15-60 minutes. In the R33 phase of this research, the utility and limitations of the integrated microscope will be evaluated by examining cells undergoing apoptosis, a process of critical importance to cancer therapy. Studies will be conducted to evaluate the ability of the instrumentation to identify subpopulations of cells at early and late phases of apoptosis induced by both chemicals and expression of specific genes. The ability of OM to guide MR measurements to specific cell populations or to neighboring populations will be determined. It is anticipated that the successful development of this instrumentation will, ultimately, greatly enhance the speed, specificity and utility of noninvasive MR methods in cancer research.